<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>

<style>

    .div_overlay
{
            display:black;
            position: fixed;
            top: 0%;
            left: 0%;
            width: 100%;
            height: 100%;
            background-color: black;
            z-index:1010;
            -moz-opacity: 0.8;
            opacity:.80;
            filter: alpha(opacity=80);
}

.div_content
   {
            display:black;
            position: fixed;
            top: 50%;
            left: 50%;
            width: 480px;
            margin-left:-240px;
            height: 300px;
            margin-top:-150px;
            padding: 0;
            border: 12px solid #3777BC;
            background-color: #F0F5F8;
            _position:absolute;
            z-index:1011;
            overflow: hidden;
}

</style>


<body>
123123
<div class="div_overlay"> </div>
<div class="div_content"> 1212</div>
</body>
</html>